A vehicle mounting a power train referred to as a hybrid system, in which an engine (possibly a known mechanism such as a gasoline engine or a diesel engine) and a motor are combined, has been developed and commercially available. Further, a vehicle (electric vehicle, fuel cell electric vehicle) mounting a power train using only the motor as the running source and not mounting any engine, has also been developed. In such a vehicle, the motor functions as a generator at the time of braking of the vehicle to provide regenerative energy, and the regenerative energy charges an electric storage mechanism (a battery or a capacitor) for motor driving. Consequently, kinetic energy of the vehicle is recovered as electric energy, and regenerative braking force acts on the vehicle. In order to prevent any damage caused by excessive charging of electric storage mechanism, it is necessary to prevent generation of regenerative energy and to stop charging power to the electric storage mechanism, before the electric storage mechanism is fully charged. By such an operation, the regenerative braking force that has acted until then is lost, and the driver may feel something is wrong. Japanese Patent Laying-Open No. 11-343890 discloses a technique of preventing change of braking feeling, by allowing regenerative braking while the capacitor is in a fully charged state.
The controller disclosed in Japanese Patent Laying-Open No. 11-343890 is a purge controller of a canister in a hybrid vehicle including an engine generating driving force for running, a motor generating the driving force for running as well as regenerative braking force, and an electric storage mechanism supplying electric power for driving the motor and charged with the regenerative power generated by the motor. The controller includes a canister adsorbing evaporated fuel from the engine, a heater for heating the canister to purge evaporated fuel adsorbed by the canister, a remaining capacity detecting unit detecting the remaining capacity of the electric storage mechanism, and a purge control unit supplying regenerative power generated by the motor to the heater if the remaining capacity of the electric storage mechanism detected by the remaining capacity detecting unit is equal to or higher than a prescribed threshold value.
According to the controller disclosed in Japanese Patent Laying-Open No. 11-343890, when the remaining capacity of the electric storage mechanism detected by the remaining capacity detecting unit is smaller than the prescribed threshold value and charging of the electric storage mechanism is still possible, the electric storage mechanism is charged with the regenerative power generated by the motor through regenerative braking, and the kinetic energy of the vehicle body can be recovered as electric energy. If the remaining capacity is equal to or larger than the prescribed threshold value and further charging of the electric storage mechanism is impossible, the regenerative power generated by the motor through regenerative braking is supplied to the heater and can be used for purging evaporated fuel adsorbed in the canister. Therefore, regardless of the amount of remaining capacity of the electric storage mechanism, the motor can always execute regenerative braking. Accordingly, wasteful energy consumption can be prevented and the change of braking feeling can be avoided.
In the controller disclosed in Japanese Patent Laying-Open No. 11-343890, however, it is sometimes unnecessary to purge the evaporated fuel adsorbed in the canister, and actually, considering durability of the heater, frequency of supplying regenerative power to the heater is limited. Therefore, it is not always possible to avoid the change of braking feeling experienced when the regenerative braking force decreases.